| Month | Temp. (min) | Temp. (max) | Temp. (avg) | Precipitation |
| January | 32°F | 47°F | 38°F | 4.1" |
| February | 33°F | 53°F | 42°F | 3.0" |
| March | 38°F | 60°F | 48°F | 4.8" |
| April | 39°F | 61°F | 50°F | 2.9" |
| May | 45°F | 70°F | 57°F | 4.8" |
| June | 48°F | 72°F | 59°F | 2.1" |
| July | 53°F | 83°F | 68°F | 1.3" |
| August | 51°F | 84°F | 67°F | 1.2" |
| September | 44°F | 75°F | 59°F | 2.8" |
| October | 42°F | 61°F | 50°F | 3.8" |
| November | 33°F | 52°F | 42°F | 7.5" |
| December | 33°F | 45°F | 39°F | 11.3" |
| Index | Gaston | Oregon | National |
| Air quality index | 38 | 32 | 42 |
| Pollution index | 3,182,180 | 7,156,356 | 2,726,193 |
| Measurement | Total |
| Days measured | 365 |
| Days with good air quality | 285 |
| Days with moderate air quality | 77 |
| Days w/ poor A.Q. for sensitive groups | 3 |
| Days with unhealthy air quality | 0 |
| Pollutant | Total |
| Arsenic | 0.010% |
| Benzene | 0.040% |
| Carbon Tetrachloride | 0.030% |
| Lead | 0.190% |
| Mercury | 0.110% |
| City | Population | Air Quality Index | National Avg. |
| Dayton, OR | 2,726 | 32 | 36.0% |
| Carlton, OR | 2,135 | 32 | 36.0% |
| Donald, OR | 1,465 | 32 | 36.0% |
| Lafayette, OR | 4,222 | 32 | 36.0% |
| Dundee, OR | 3,296 | 32 | 36.0% |
| Gaston, OR | 526 | 38 | 24.0% |
| City | Population | Air Quality Index | National Avg. |
| Fox River, AK | 526 | 31 | 38.0% |
| Danville, MD | 526 | 36 | 28.0% |
| Polkville, NC | 526 | 36 | 28.0% |
| Old Green, OK | 526 | 36 | 28.0% |
| Petros, TN | 526 | 53 | 6.0% |
| Gaston, OR | 526 | 38 | 24.0% |
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